Human milk is an irreplaceable food for the newborn. However, on many occasions, due to illness of the mother, bad quality of milk secretion, or even due to specific social and/or economic factors, the newborns are to fed with milk formulas which try to be similar, both in qualitative and quantitative aspects, to human milk.
The European Paediatrics Society for Gastroenterology and Nutrition, EPSGAN, issued in 1978 some rules that humanized milk formulas for the feeding of infants must comply with. In the same way, in 1976 the American Academy of Paediatrics, AAP, published the standards for the formulation of baby foods as substitutes of human milk.
These standards state the maximum and minimum content in proteins, lipids, glucides, mineral salts and vitamins of a humanized milk formula, for the feeding of healthy infants. Likewise the EPSGAN prescribed that this kind of artificial milk, produced mainly with cow's milk and milk by-products, must keep a casein/lactalbumin ratio of about 40:60, which is similar to the one found in human milk. They also must have a fatty acid pattern most resembling, both in qualitative and quantitative aspects, the one found in human milk.
Despite all the scientific efforts carried out, until now it has been impossible to find a product which has the same composition of human milk. This is due mainly to the presence of specific microcomponents in human milk which even can be different according to each person. An example of these components are the immunoglobulins of secretory character which give to the milk of each mother specific antibodies against many illnesses. These antibodies protect the infant during the first months of his life against those same illnesses that the mother has undergone.
Among the microcomponents of milk there are other substances which have an unknown structure and physiology.
Nucleotides are fundamental substances for life, as they are structural units of the nucleic acids, which are the responsible compounds of the individual genetical load. Even when nucleotides take part in many biochemical reactions, their function in milk remains unknown. There are few studies carried out to find out the nucleotidic composition of milk from different species, being limited to the chromatographic analysis of some individual samples, which does not allow any conculsions to be drawn without a risk of error.
Before going further, it will be convenient to set up some equivalences between terms used in this description. Accordingly, "humanized milk" will be understood as a milk artificially treated ("adapted milk") to become similar to human milk; "breast milk" will be equivalent to "human milk".
Regarding the identification of the different kinds of nucleotides, it will be used, as it is extended in practice, the abbreviated name formed by the respective initials.
AMP=Adenosine-monophosphate PA0 CMP=Cytidine-monophosphate PA0 GMP=Guanosine-monophosphate PA0 IMP=Inosine-monophosphate PA0 UMP=Uridine-monophosphate PA0 ADP=Adenosine-diphosphate PA0 CDP=Cytidine-diphosphate PA0 UDP=Uridine-diphosphate PA0 ATP=Adenosine-triphosphate PA0 UTP=Uridine-triphosphate PA0 NAD=Nictine-adenin-dinucleotide PA0 UDPG=Uridine-diphosphate-glucose PA0 UDPGa=Uridine-diphosphate-galactose PA0 UDP-N-AG=Uridine-diphosphate-N-acetyl-glucosamine PA0 UDP-N-AGa=Uridine-diphosphate-N-acetyl-galactosamine PA0 GDPMan=Guanosine-diphosphate-mannose PA0 GDPFuc=Guanosine-diphosphate-fucose